GB2223967A

GB2223967A - Finishing bevel gear tooth surfaces

Info

Publication number: GB2223967A
Application number: GB8919810A
Authority: GB
Inventors: Norio Hosoya; Shigeyuki Yoneyama
Original assignee: KOGANEI SEIKI SEISAKUSHO KK
Current assignee: KOGANEI SEIKI SEISAKUSHO KK
Priority date: 1988-09-01
Filing date: 1989-09-01
Publication date: 1990-04-25
Also published as: IT8921420A0; US4982532A; DE3929106A1; JPH0271919A; GB8919810D0; IT1231095B; FR2635705A1

Description

FINIShING JAEVBL GEAR TOOTH SURFACES This invention relates to a method

and an apparatus for finishing gear tooth surfaces of a bevel gear.

As a prior art for finishing a gear surface of a bevel gear, United States patent 3,740,899 discloses a method, as shown in Fig. 7 of this application, where the bevel gear 12 is rocked along arrow 30 to perform a lap finishing. The rocking direction of the engaging gear teeth is shown by arrow 30'.

On the other hand, United States patent 2,904,934 discloses another example of lap finishing where, as shown in Figure 8, the bevel gears are rocked along the gear trace direction 3V.

According to one aspect of the invention there is provided a method for finishing bevel gears, comprising the steps of: rotatably supporting a first bevel gear; rotatably supporting a second bevel gear meshing with the first bevel ge,-i-:; 20 rotating at least one of the first and second bevel gears while providing a brake force between them; and providing a rocking motion generally along or tangentially to a tooth profile direction extending 25 between the top and the root of an instantaneously engaging gear tooth of at least one of the first and second bevel gears in such a manner that it swingably rocks about the vertex of its base pitch cone, so that the contacting gear tooth surfaces of at least one of 30 the gears are finished by both the reciprocal sliding contact and the said rocking motion. According to another aspect of the invention there is provided an apparatus for finishing bevel gears, comprising: means for rotatably supporting a first bevel gear; 2 '. 22 2_) 3Y 9 6 7 means for rotatably supporting a second bevel gear, engaged with said first bevel gear in a meshing fashion; means for rotating at least one of the bevel gears while imparting a brake force between them; and means for providing a rocking motion generally along or tangentially to a tooth profile direction extending between the top and the root of an instantaneously engaging gear tooth of at least one of the first and second bevel gears in such a manner that it swingably rocks about the vertex of its base pitch cone, so that, in use, gear tooth surfaces of at least one of the gears are finished by both the reciprocal sliding contact and the said rocking motion.

In both of the prior art patents mentioned above, the rocking motion is not generated in a manner such that it has a pivot centre which is the vertex of a base pitch circle cone of at least one of the gears. Thus, the finished product is not finished to a high tolerance and also has the disadvantages of higher noise and lower productivity.

In the apparatus of the invention, the rocking means may include a plate on which one of the gears is supported, the plate being pivotable about an axis passing through the vertex of the base pitch circle cone.

For a better understanding of the invention, embodiments of it will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 illustrates a plan view of the apparatus of the invention; Figure 2 illustrates a cross-sectional view taken along line II-II of Figure 1; Figure 3 illustrates a side elevation view of Figure 1; J 1 Figure 4 illustrates another embodiment of the apparatus of Figure 2; Figure 5 illustrates the principle of the invention; Figure 6 illustrates a cross-sectional view taken along line VI-VI in Figure 5; Figure 7 illustrates a prior method for finishing a bevel gear; and Figure 8 illustrates another prior method for finishing a bevel gear.

The detailed description of the invention is hereinafter explained with reference to Figures 1 - 6.

The principle of the invention is schematically shown in Figure 5. The bevel gears 11 and/or 12 are relatively rocked around their common pivot axis 18 which is positioned at the vertex 19 of the base pitch circle cone such that each of them is relatively rocked along a sectional arc.

In Figures 1 - 3, 1 denotes a bed, 2 a column, 3 a vertical movement saddle, 4 a first support box, 5 an angle adjustment saddle, 6 a swivel base, 7 a swingably movable rock plate, and 8 a second support box.

In this apparatus, the bevel gears 11 and 12 are each adjustably supported by a conventional means so as to be movable in directions given by arrows 13, 14, 16, 22 and 23. The vertex 19 of the base pitch circle cone is located on the axis of the pivot shaft 18.

The first bevel gear 11 is rotated about a support axis 51 of the first support box 4 as it is driven by a motor 24 and adjusted along arrows 13 and 22 in such a manner that the vertex 19 is positioned on the extension of the axis of rotation 21 of the angle adjustment saddle 5 as well as on a support axis 52 of the second support box 8.

Then the second bevel gear 12 is rotatably mounted about the support axis 52 of the second support box 8 and is adjusted along arrow 14 so that the vertex 19 is positioned on the axis of the pivot shaft 18 and is further adjusted along arrow 16 so as to make angle 53 a right angle, for instance, as shown in Figure 1.

Further, a brake means comprising a brake member and a disc 9 fixed on the support axis 52 of the bevel gear 12 is provided for generating an adequate contact pressure between engaging gear teeth of the bevel gears 11 and 12.

The rock plate 7 is swingably rocked by an eccentric cam on a shaft 17 driven by a flexible shaft about the pivot shaft 18 positioned in the swivel base 6. As a result, the second bevel gear 12 rocks against the first bevel gear 11 as shown by curved arrow 15', generally in or tangentially to the direction of the tooth profile (involute line) between the top and the root of one of the pair of instantaneously engaging teeth during rotation of gears 11 and 12 about their respective axes 51 and 52.

The rock plate 7 is supported by, for example, an air bearing and is rocked between the swivel base 6 and a guide plate 25, as shown generally by arrow 15.

The stroke of the rocking motion of the bevel gear 12 along arrow 15' is adjusted such that adequate contact is produced between bevel gears 11 and 12.

Thus, the bevel gear 12 moves back and forth with respect to the bevel gear 11.

According to the lap finishing of this method ' and the apparatus, both reciprocal lap finishing by the meshing workpiece bevel gears 11 and 12 as thay rotate and the lap finishing by the rocking motion about the vertex are simultaneously performed and, as a result, an ideal and rational finishing is performed.

The arrow 15 shows the rocking movement direction when both gears are rocked not along the pressure angle. If the swivel base 6 is rotated along arrow 23 1 1 in Figure 3 by an angle corresponding to the pressure angle 26 (arrow 28 in Figure 6) or 26' (reverse arrow 28') about the support axis 52 containing the vertex 19 the direction of the rocking motion is now given by arrow 27 (27') along the pressure angle, and a further ideal lap finishing is performed.

If the pivot shaft 18 is also provided with a small amount of eccentricity, for example from 0.01 mm to 0.2 mm, the contact between two gear surfaces becomes more smooth.

Figure 4 shows another embodiment of rock plate 7' which has another pivot shaft 18'. In this embodiment either pivot shaft 17 or 18' can be a rocking motion generator or a pivot shaft.

The above embodiments of the invention have been concerned with reciprocal finishing between two workpiece bevel gears 11 and 12, however, one of them can be replaced by a master bevel gear having a sufficient hardness, precision and finishing ability to finish the other gear, which is the workpiece gear.

The bevel gears 11 and 12 produced by the embodiments of Figures 1 to 4 must be used as a pair in order to obtain a correct meshing. However, by the method of using a master bevel gear, a reciprocal bevel gear can be obtained and, therefore, it should not be used as a pair.

The master bevel gear its elf can be, for instance, one on which diamond powders are deposited on the gear surface by electro-deposition or the like. It also can be one which is formed into a-bevel gear shape. When using the master bevel gear, cutting oil such as machine oil can be used. It is more effective to provide ultrasonic vibration when lapping liquid or machine oil is used.

This apparatus can also be applied to hypoid gears and others.

In summary, since the bevel gear 12 is rocked along an arc, the finishing of the gear surface becomes more ideal and the finishing accuracy is distinctly improved. Also, the noise of the finished gears is 5 remarkably reduced and productivity is increased.

For further information reference is made to the applicant's prior application GB 2208495.

Claims

1. A method for finishing bevel gears, comprising the steps of:

rotatably supporting a first bevel gear; rotatably supporting a second bevel gear meshing with the first bevel gear; rotating at least one of the first and second bevel gears while providing a brake force between them; and providing a rocking motion generally along or tangentially to a tooth profile direction extending between the top and the root of an instantaneously engaging gear tooth of at least one of the first and second bevel gears in such a manner that it swingably rocks about the vertex of its base pitch cone, so that the contacting gear tooth surfaces of at least one of the gears are finished by both the reciprocal sliding contact and the said rocking motion.

2. A method according to claim 1, wherein the first and second bevel gears are both workpiece gears.

3. A method according to claim 1, wherein one of the bevel gears is a master bevel gear and the other bevel gear is a workpiece bevel gear.

4. A method according to any preceding claim, further comprising the step of adjusting the meshing angle of one of the first and second bevel gears with respect to the other so as to give a pressure angle between them.

5.

comprising:

An apparatus for finishing bevel gears, means for rotatably supporting a first bevel gear; means for rotatably supporting a second bevel gearf engaged with said first bevel gear in a meshing fashion; means for rotating at least one of the bevel gears while imparting a brake force between them; and means for providing a rocking motion generally along or tangentially to a tooth profile direction extending between the top and the root of an instantaneously engaging gear tooth of at least one of the first and second bevel gears in such a manner that it swingably rocks about the vertex of its base pitch cone, so that. in use. gear tooth surfaces of at least one of the gears are finished by both the reciprocal sliding contact and the said rocking motion.

6. An apparatus according to claim 5, wherein the first and second bevel gears are both workpiece gears.

7. An apparatus according to claim 5, wherein one of the bevel gears is a master bevel gear and the other bevel gear is a workpiece gear.

8. An apparatus according to any of claims 5 to 7 and further comprising means for adjusting the meshing angle of one of the first and second bevel gears with respect to the other so as to give a pressure angle between them.

9. An apparatus according to any of claims 5 to 8, in which the means for providing the rocking motion includes a rock plate for supporting one of the bevel gears, pivotably mounted about an axis passing through the pitch cone vertexand a means for providing the rocking motion via an eccentric cam located in the rock plate at a point distant from its pivot axis.

10. A method substantially as described herein with reference to the accompanying drawings 1 to 6.

11. An apparatus substantially as described herein with reference to the accompanying drawings Published 1990 atThe Patent Office.State House, 66.71 High Holborn, London WC1R 4TP. Further copies maybe obtained from The Patent OffIceSales Branch. St Mary Cray, Orpington. Kent BR5 3RDPrinted by Multiplex techniques ltd. St Mary Cray. Kent. Con. 1187